The present invention relates to a shock absorber preferably used to damp an oscillation of, for example, an automobile and a rail vehicle.
As a shock absorber used for an automobile, a rail vehicle, and the like, there is known a double tube damper configured in such a manner that an interior of a cylinder is divided into a rod-side chamber and an opposite rod-side chamber (a bottom-side chamber) by a piston, and a reservoir chamber is defined outside the cylinder. As a kind of such a damper, there is a biflow-type shock absorber (damper) in which hydraulic fluid in the rod-side chamber is transmitted into the reservoir chamber in one direction and hydraulic fluid in the reservoir chamber is also transmitted into the opposite rod-side chamber in the one direction during an extension stroke of a piston rod. During a compression stroke of the piston rod, hydraulic fluid in the opposite rod-side chamber is transmitted into the reservoir chamber in another direction and hydraulic fluid in the reservoir chamber is also transmitted into the rod-side chamber in the other direction. Therefore, as disclosed in Japanese Patent Application Disclosure No. 2003-74614, a suction valve of poppet valve type is provided at a rod guide that slidably supports the piston rod.
The biflow-type double-tube shock absorber according to the above-described conventional technique delivers the hydraulic fluid from the reservoir chamber into the rod-side chamber as if sucking it by opening the suction valve of poppet valve type during the compression stroke. However, the hydraulic fluid may be unable to be sucked sufficiently at this time, whereby a plurality of suction valves (poppet valves) has to be provided to ensure sufficient suction. Therefore, the conventional technique has such a problem that not only the plurality of suction valves increases cost of the shock absorber but also obtaining a space for mounting these suction valves within the rod guide makes a size reduction of the shock absorber difficult.